JavaScript Interview Questions

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What is JavaScript?

JavaScript is a client-side as well as server side scripting language that can be inserted into HTML pages and is understood by web browsers. JavaScript is also an Object based Programming language.

What is the difference between JavaScript and Java?

Java is an Entire programming language. In Distinction, JavaScript is a coded program that can be popularized to HTML pages. These 2 languages are not at all inter-dependent and are designed for different intent. Java is an object-oriented programming (or) structured programming languages like C++ or C whereas JavaScript is a client-side scripting language. – What is Java?

What are JavaScript Data Types?

The JavaScript Data types

Number

String

Boolean

Object

Undefined

What are the Different Types of Scope Chain Available in JavaScript?

If we check in the program, every local scope has a connection with one or more scope in their back which forms a chain. This chain goes on until it met with the global scope which is the root of this hierarchy. As global scope doesn’t have a parent, so it is on the top of the chain. This is known as the scope chain. The scope chain in JavaScript is basically used to resolve the values of the variable. Without this, it is difficult for a JavaScript to choose a certain value for a variable if there are many variables defined at different scopes.

How do we add JavaScript onto a web page?

There are more ways for adding JavaScript on a web page, but there are two ways which are commonly used by developers If your script code is very short and only for a single page, then following ways are the best:

You can place the tag inside the <head> element.<head><title>Page Title</title><script language="JavaScript" type="text/JavaScript"> Var name = "onlineitguru" Alert (name);</script></head>

What is the use of is NaN function?

Is Nan function returns true if the argument is not a number otherwise it is false?

Explain MUL Function In JavaScript?

MUL means simple multiplication of numbers. It is a technique in which you pass a one value as an argument in a function and that function returns another function to which you pass the second value and the process go on. For example: x*y*z can be representing as:

‘SessionState‘ is Exact to user-specific data that can be accessed across all pages in the web application.

Does JavaScript support automatic type conversion?

Yes JavaScript does Encourages automatic type conversion, it is the frequent way of type conversion used by JavaScript developers

What are all the looping structures in JavaScript?

They Are 3 looping structures in JavaScript:

For

While

do-while loops

Explain how to read and write a file using JavaScript?

There are 2 ways to read and write a file using JavaScript

Using JavaScript extensions

Using a web page and Active X objects

Explain Promise In JavaScript?

A promise is an object in JavaScript which is used to produce a value that may give result in the future. The value can be resolved value or it can be a reason which tells why the value is not resolved.

A promise can be of three states:

Fulfilled: The operation is completed and the promise has a specific value.

Rejected: The operation is failed and promise has a reason which shows why the operation failed.

Pending: The operation is not fulfilled or rejected, means it has not completed yet.

What is called Variable typing in JavaScript?

Variable typing is used to assign a number to a variable and the similar variable can be assigned to a string.

i = 10;i = "string";

Consider the following statements and tell what would be the output of the logs statements?

It is easy to add an advanced property in an existing function by just giving value to the existing function it. For example, let us have an Actual object person, to give new property check the below code:

The Input Give by any user in the JavaScript is entered with the help of a prompt box. While putting progressive the data or the input, the prompt box allows the user to do so with the help of a text box. To include the number, label box is also used.

What is an undefined value in JavaScript?

Undefined value means the:

Variable used in the code doesn’t exist

Variable is not assigned to any value

The property doesn’t exist

Define event bubbling?

JavaScript Enters DOM elements to be nested inside each other. Once choice of the, if the handler of the child is clicked, the handler of the parent will also work as if it were clicked too.

JavaScript Code Implementation?

There are 3 ways to add JavaScript commands to your Web Pages:

Embedding code

Inline code

External file

What are JavaScript Cookies?

A function that is stated without any named identifier is known as an anonymous function. In general, an unidentified function

Is inaccessible after its declaration.

Unidentified function declaration:

Var wcg = function () {Alert (’I am unidentified’);};wcg ();

What is ‘this’ keyword in JavaScript?

‘This’ keyword refers to the object from where it was called.

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